NEWS FROM THE DELAWARE DEPARTMENT OF NATURAL RESOURCES AND ENVIRONMENTAL CONTROL and THE U.S. ARMY CORPS OF ENGINEERS

Oct. 1, 2009
Vol. 39, No. 395

For more information, contact Kevin Kalasz, Delaware Natural Heritage & Endangered Species Program, 302-653-2880; Bartholomew Wilson, Delaware Coastal Programs, 302-739-9161; Joanna Wilson, DNREC Public Affairs, 302-739-9902; or Richard Pearsall, U.S. Army Corps of Engineers Public Affairs, 215-656-6032. PHOTOS AVAILABLE.

Army Corps, DNREC team up on Mispillion Inlet
navigational maintenanceand habitat restoration project

What began as a routine navigational maintenance project for the U.S. Army Corps of Engineers in cooperation with the Delaware Department of Natural Resources and Environmental Control also provided an ideal opportunity to partner in protecting a vital natural resource: horseshoe crab/migratory shorebird habitat in Mispillion Harbor. That fragile but crucial habitat was threatened by a breach in the man-made breakwater that shelters the area. By combining their skills, the two agencies were able to use dredging equipment for the dual purpose of channel maintenance and breakwater restoration in one efficient month-long project that was just completed Sept. 29.

“This was a tremendous opportunity for the State of Delaware and the Army Corps of Engineers to come together and protect this invaluable resource. The partnership that was developed through the course of this project should be a testament and model of how well federal and state agencies can interact to preserve and restore our coastal resources,” said DNREC Secretary Collin O’Mara.

 “This is essentially two projects for the price of one,” said Lt. Col. Thomas Tickner, Philadelphia District Commander for the Army Corps. “We solved one problem by taking excess sand out of the inlet, then teamed with DNREC to solve another by placing that same sand to help rebuild a habitat.” According to Charles Myers, the Army Corps’ Mispillion River project manager, the dredged sand will be reused both to restore the valuable red knot/horseshoe crab environmental area and to protect the jetty on Conch Bar Island.

Back in June, as DNREC reviewed the Army Corps of Engineers’ permit request for maintenance dredging, the breach was discovered at the north end of the Mispillion breakwater protecting the Mispillion River and Harbor. Tidal flow through the breach was accelerating erosion of the state’s most valuable habitat for spawning horseshoe crabs and foraging shorebirds, a sandy beach directly across from the DuPont Nature Center at the mouth of the Mispillion River. Now owned by the DNREC Division of Fish and Wildlife, the area was artificially created through past navigational projects which constructed the breakwater and inlet jetties, and now requires periodic maintenance to maintain its habitat quality.

“Mispillion Harbor routinely has the highest horseshoe crab egg densities in the Delaware Bay, attracting the greatest concentration of red knots and other shorebirds to its shores. This makes the area one of the most important sites for shorebird conservation not only in Delaware but also in the entire Atlantic Coast flyway. This project was critical to preserving the habitat required by both horseshoe crabs and shorebirds,” said Kevin Kalasz, a wildlife biologist with the DNREC Division of Fish and Wildlife’s Natural Heritage & Endangered Species Program.

Extensive shorebird and horseshoe crab monitoring has been conducted over the past decade by the DNREC Division of Soil and Water’s Delaware Coastal Programs and the Natural Heritage & Endangered Species Program, identifying the important yet fragile nature of Mispillion Harbor. In 2008, rapidly eroding beaches prompted Delaware Coastal Programs to conduct a detailed engineering and modeling project to design options for restoring horseshoe crab and shorebird habitat and to assess their feasibility.

After the discovery of the breach, Delaware Coastal Programs surveys in early July indicated that the damage was severe and must be addressed as soon as possible. An immediate coordinated effort was initiated between the Army Corps of Engineers Philadelphia District and several DNREC programs: the Natural Heritage & Endangered Species Program, Division of Parks and Recreation’s Natural Areas Program, Division of Water Resources’ Wetlands and Subaqueous Lands Section, Division of Soil and Water’s Shoreline and Waterway and Coastal Programs sections. Federal funding was obtained through the Corps for completion of the navigational maintenance as well as the proposed restoration efforts.

The two agencies determined that filling the erosional channel and back breakwater area with course sandy sediments would curtail the tidal exchange with the Delaware Bay, and that 25,000 cubic yards of sediment would be required to fill the void and stabilize the area. To accomplish this, a large sand source had be located within 1.5 to 2 miles. Using coring equipment, remote acoustics and Delaware Bay Benthic mapping bottom and sub-bottom sediment data, Delaware Coastal Programs located a sand borrow site adjacent to the southern jetty that contained about 65,000 cubic yards of fine to coarse sand suitable for the restoration efforts.

The Army Corps of Engineers contracted Southwind Construction Corporation of Evansville, Indiana, to conduct the navigational channel maintenance along Cedar Creek and the 2,000-foot approach channel to the Inlet, plus the Mispillion Breakwater restoration work. The navigational dredging started in early September and was completed in three weeks, with channel sediments consisting of very fine grained mud deposited north of the breakwater along the beach.

Breakwater restoration began Sept. 22 and was completed Sept. 29 by pumping 25,000 cubic yards of medium to course sand from the borrow site to the interior of the breakwater. The area was graded according to beach templates designed by DNREC’s Shoreline and Waterways survey crew.